This invention pertains generally to gyroscopically stabilized equipment, and particularly to apparatus for measuring the angular relationship between a gyroscopically stabilized platform and a body in which such platform is mounted.
It is known in the art of guided missiles that gyroscopically stabilized platforms with two degrees of freedom (in pitch and yaw) may be used to advantage in guided missiles to support a sensor, as an infrared sensor or a radar antenna. Here such a platform is a rotating magnetized disk with a north and a south pole. With such an arrangement it is necessary that the pitch and yaw components of the angle between the boresight line of the sensor (which line may correspond with the axis of rotation of the gyroscopically stabilized platform) and the longitudinal axis of the guided missile be measured. The pitch component and yaw component (referred to hereinafter as the "pitch angle" and the "yaw angle") are usually measured by sensing current induced in so-called "cage coils," which current is indicative of the orientation of the gyroscopically stabilized platform (hereinafter referred to simply as "the platform"). In addition, so-called "reference coils" are provided to produce control signals for maintaining a substantially constant angular velocity of the gyroscopic mass in the platform. However, the current induced in any cage coil may result from magnetic interference generated in other necessary elements (such as drive and precession coils) on or near the platform, with the result that unacceptably large errors in the desired measurement are experienced.